This invention relates to an image formation apparatus, such as a copier or a printer, and in particular to an image formation apparatus comprising a photosensitive unit containing a photosensitive body disposed detachably in the main body of the apparatus.
Conventional image formation apparatuses are described in Unexamined Japanese Patent Publications 59-61854 and 61-147267 and Postexamined Japanese Patent Publication 1-41987, for example. Each of the conventional image formation apparatuses comprises a unit comprising devices, such as a developing device, a cleaning device, and a charger placed surrounding a photosensitive body, integral with the photosensitive body, which will be hereinafter referred to as photosensitive unit, although the unit is called in different ways a process cartridge, a process unit, a process kit, or the like, the photosensitive unit being disposed detachably in the main body of the apparatus.
With the conventional image formation apparatus, the photosensitive unit at the end of its life is replaced with a new one, thereby maintaining the image quality. Various suggestions are made as to how to measure, display, and determine the rest of the life, how to prompt the user to replace the photosensitive unit, and the like.
By the way, in the conventional image formation apparatuses, the life of the photosensitive unit is set so that the photosensitive unit is replaced with the life of the photosensitive body as the reference, thus the photosensitive body in the old photosensitive unit removed by replacement is scheduled to be only discarded and is not intended to be recycled.
However, if the photosensitive body uses a long-life material such as amorphous silicon, even if the surface is scratched to some extent, the photosensitive body can be recycled for continuing use thereof.
To thus recycle the photosensitive body, it becomes necessary to manage the fact as to whether or not the photosensitive body in the photosensitive unit removed by replacement can be recycled and whether the photosensitive body in the photosensitive unit newly mounted by replacement is a brand-new or recycled product.
When the image formation apparatus itself guarantees a reasonable number of print sheets of paper, if a counter circuit of the main body of the apparatus or a main body controller having a memory storing the cumulative number of print sheets of paper is destroyed electrically, calculation for guaranteeing the number of print sheets of paper cannot be executed.